Oligomers of hydrolyzed acrylamide-sulfur dioxide copolymers

ABSTRACT

A novel class of oligomers of hydrolyzed acrylamide-sulfur dioxide copolymers are disclosed.

United States Patent [191 Panzer et al.

[451 Feb. 4, 1975 [54] OLIGOMERS 0F HYDROLYZED C YLAl l LE DIQJQDE COPOLYMERS [75] Inventors: Hans Peter Panzer, Stamford;

William Charles Firth, Jr., Wilton; Anthony Thomas Coscia, South Norwalk; Lucille Elma Palmer, Darien, all of Conn.

[73] Assignee: American Cyanamid Company,

Stamford, Conn.

221 Filed: Sept. 11, 1913 21 Appl. No.2 396,167

Related US. Application Data [62] Division of Ser. No. 134,057, April 14, 1971, Pat.

[52] US. Cl. 260/5l3.7, 260/513 N, 260/557 R [51] int. Cl C07c 145/00 [58] Field of Search 260/513.7, 79.3 R

[56] References Cited UNITED STATES PATENTS 12/1937 Snow 260/513 R 8/1972 Keim 260/79.3 A

OTHER PUBLlCATlONS Cram et al., Organic Chemistry", 2nd edition, pp. 103-105 (1964).

Primary Examiner-Leon Zitvcr Assistant Examiner-Nicky Chan Attorney, Agent, or Firm-Frank M. Van Riet 1 OLIGOMERS F HYDROLYZED ACRYLAPYHPE-SULFURDIQXIDE. co ouusss CROSS-REFERENCE TO RELATED APPLICATIONS This application is a division of our copending application, Ser. No. 134,057, filed Apr. 14, 1971, now U.S Pat. No. 3,792,027 and entitled NOVEL COPOLY- MERS.

BACKGROUND OF THE INVENTION The present invention pertains to the field of polymeric materials and, more particularly, to the field of polymeric materials which may be utilized to impart improved wet and dry-strength properties to paper. The polymers are produced from acrylamide and sulfur dioxide and,,when reacted with glyoxal, result in the production of a series of materials which unexpectedly impart a high degree of wet and dry-strength to paper.

Many olefins have been found to copolymerize with sulfur dioxide to form polysulfones, lvin, et al, Advances in Macromolecular Chemistry, Vol. 1, Academic Press, N.Y., pp. 335-406. The presence of various substituents such as carbonyl groups or nitrile groups, however, being electronegative, can prevent polymerization. It was therefore unexpected that acrylamide and sulfur dioxide copolymerize readily even though cyclopentene, acrylamide and sulfur dioxide have been known to form terpolymers, Iwatsuki et al, .I. Poly. Sci., Part A-l, Vol. 6, page 2451, 1968. Japanese Patent No. 9971. 1965 (Chem. Abstracts, Vol. 64,

page 3799, 1966) teaches the copolymerization of acrylamide and sulfur dioxide by irradiation at low temperatures, however, a subsequent report (Kuri, Kobunshi, Vol. 18, pages 106-203, 1969) indicates that a similar system produced a copolymer containing only one percent sulfur.

i We have now found that copolymers of acrylamide and sulfur dioxide can be prepared wherein the polymers contain a high percentage of sulfur. The polymers are easily recovered in relatively good yields.

SUMMARY The novel acrylamide-sulfur dioxide copolymers of our invention find utility in the improvement of both the wet-strength and the dry-strength of paper, especially that composed of water-laid cellulose papermaking fibers. The polymers function as wet and drystrengthening agents after having been reacted with glyoxal, with or without the addition of an anionic charge imparting substituent and preferably in the presence of a retention aid, as more fully described hereinbelow.

DESCRIPTION OF THE INVENTION INCLUDING PREFERRED EMBODIMENTS The polymers of the present invention have the formula wherein the ratio of x to y ranges from about 10:1 to about 2:1, n is a whole positive integer ofa least about 6, the polymer containing up to about 7.5 percent. by weight, based on the total weight thereof, of sult'onate groups. i.e. SO

The polymers are produced by heating the acrylamide in liquid sulfur dioxide at a temperature ranging from about 25C. to about C. under sufficient pressure to render and maintain the sulfur dioxide liquid.

The polymerization is conducted in the presence of a free-radical generating catalyst. From about 0.01 to about 5.0 percent of the catalyst, by weight, based on the total weight ofthe monomers, may be used. with an amount ranging from about 0.1 to about 3.0 percent. by weight, same basis, being preferred.

Generally, any known free-radical generating catalyst may be employed with such compounds as methyl ethyl ketone peroxide, benzoyl peroxide, azobisisobutyronitrile, silver nitrate, calcium nitrate, cerous nitrate, ammonium nitrate, ceric ammonium nitrate, lauroyl peroxide, 2,5'dimethyl-2,5-di(t-butylperoxyl-nhexane, dialkyl peroxides such as diethyl peroxide, di(t-butyl)peroxide, t-butyl hydrogen peroxide, cumene hydroperoxide, t-butyl perbenzoate and the like being exemplary.

The polymerization reaction should be allowed to continue for from about 1 hour to about 7 days, preferably from about 5 hours to about 3 days. The time of reaction is directly dependent upon the catalyst concentration and the temperature of reaction, lower temperatures and lower catalyst concentrations requiring longer reaction times.

The reaction should be conducted in the substantial absence of oxygen in order to assure best results. Oxygen can be excluded from the reaction vessel by any known means such as by evacuation, nitrogen blanket CtC.

Up to about 10 percent, by weight, ofthe novel polymers of our invention can be a monoethylenically unsaturated acyclic monomer copolymerizable with the acrylamide and sulfur dioxide. For example, such monomers as methacrylic acid, itaconic acid, acrylic acid, the lower acrylic and methacrylic esters such as ethyl acrylate, methyl methacrylate etc., acrylonitrile, methacrylamide, etc. may be charged to the reaction vessel with the acrylamide and sulfur dioxide. Use of comonomers of this type is advantageous when various properties of the resultant polymer not possessed by the acrylamide-sulfur dioxide copolymer alone, are desired.

The novel polymers of our invention may contain up to about 7.5 percent, by weight, based on the total weight of the polymer, of sulfonate groups, i.e., SO;, The presence of these groups results from various manipulations made during the polymerization. That is to say. ifthe reaction is conducted at a temperature rangintroduced into the polymer. The polymers of this invention are recovered from ether.

The polymers are solid and become molten between 216C. and 226C. with gas evolution. They are generally insoluble in cold water but copolymers having high concentrations of acrylamide and low inherent viscosities. indicative of low molecular weight, are substantially water soluble. All polymers are substantially soluble in dimethyl sulfoxide and hot water.

Additionally, we have found that the polyacrylamide sulfones, i.e. the copolymers of acrylamide and sulfur dioxide discussed hereinabove, represent unique starting materials useful in the preparation of short chain (low molecular weight) aninoic polymers or oligomers by selective cleavage, of the sulfur-carbon bonds, ofthe acrylamide-S polymer chain with alkali, and simultaneous hydrolysis of carboxylamide groups to carboxyl groups. Infrared analysis shows that the original sulfone links end up as sulfinic acid moities probably located at the end of the now short organic polymer chains. Accordingly, depending on the acrylamide/S0 ratio of the starting material, that is, the average sequence distribution of the monomers in the copolymer. low molecular weight oligomers of defined chain length can be made. These low molecular weight oligomers are useful as antiprecipitants for calcium sulfate and carbonate, a dispersant for clays, silt, scale etc. and as sequestering agents and/or surface active materials.

Our novel oligomers have the general structure:

coon

caca so n COOI'I err-ea wherein n is a whole positive integer of 19, inclusive and M is an alkali or alkaline earth metal.

They are produced by contacting the acrylamide-S0 copolymer charge material with a slight excess of hydroxide, carbonate etc. at a temperature ranging from about 50C. to about 120C. in an aqueous media. The amount of hydroxide, carbonate etc. employed is dependent upon the desired amount of cleavage of the copolymer. If total cleavage is to be accomplished, one mole of hydroxide, carbonate etc. per mole of acrylamide and one mole of hydroxide, carbonate etc. per mole of $0 in the copolymer should be used. Lesser amounts of carbonate, hydroxide etc. may be used if less than total cleavage of the charge copolymer is required.

The copolymer is allowed to remain in contact with the aqueous solution of carbonate, hydroxide etc. for

from about minutes to 24 hours. preferably from about 2 hours to about '18 hours.

The solution is then allowed to dry by evaporation ol the water, neutralization thereof to about a pH of 7.0

being conducted, if desired, and the resultant powdery oligomer then remains.

Examples of suitable compounds useful in producing the novel oligomers of the instant invention include sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, barium hydroxide. calcium hydroxide and the like.

The following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by weight unless otherwise indicated.

EXAMPLE I To a suitable glass pressure reaction vessel are added 19.98 parts of acrylamide and 0.170 part of azobisisobutyronitrile. The vessel is cooled with liquid nitrogen, evacuated and brought to atmospheric pressure with dried nitrogen three times. The reactor is evacuated and 67.2 parts of sulfur dioxide are added by transfer through a vacuum line. The resultant mixture is heated to 50C. for 8 hours and allowed to stand 16 hours at room temperature. The reactor is cooled. the product washed with cold methanol, collected on a filter. washed again with methanol and dried in vacuo at room temperature and finally at 74-80C. in vacuo for 18 hours. 20 Parts of a white solid powder of copolymer is recovered. The copolymer has an inherent viscosity determined at 30C., 0.5 percent concentration. of 0.56 in dimethyl sulfoxide. Analysis shows 39.34 percent carbon, 6.05 percent hydrogen, 14.97 percent nitrogen, 8.94 percent sulfur. The averaged weight percent acrylamide is 76.78 and 17.86 weight percent sulfur dioxide. Sulfur dioxide bands (cm.) at 1305 and 1 128, carbonyl bands at 1665 and amino bands at 3440, 3365, 3205 and 1615 are detected.

EXAMPLE 2 A mixture of 3.0 parts of acrylamide, 0.024 part of azobisisobutyronitrile, 8.0 parts of sulfur dioxide and 7.1 parts of methanol is heated in a sealed glass pressure reactor for 16 hours at 50C. The resultant white, powdery product is washed with methanol and dried in vacuo at C. It is soluble in water and gives an acidic reaction. The infrared spectrum shows strong S0 absorptions at l 128 and 1305 cm. and strong bands in the I 180 and 1040 cm. region, indicating ionic sulfonate; Titration to the thymol blue endpoint gives a sulfonate content of 7.5 percent.

Following the procedure of Example 1, various other polymerization reactions with acrylamide and sulfur dioxide are conducted. The catalysts employed are varied as are the reaction conditions as indicated. The results are set forth in Table 1, below.

TABLE I Parts Parts Reaction Parts Inherent Ex. Acrylamide S0 Catalyst Parts Time Temp. Polymer Viscosity" 3 1.0 7.2 Benzoyl Peroxide .013 1 day 25C. 0.14 4 15.0 31.5 Cerous Nitrate .027 5 days 25C. 16.0 0.76 5 15.0 46.0 Ammonium Nitrate .060 18 hours 25C. 10.9 0.49 6 1.98 8.3 MEKP .025 5.5 hours 50C. 0.85 0.51 7 3.75 12.6 AIBN .032 8 hours 50C. 4.3 0.52 8 10.0 50.0 AIBN .085 5 hours 80C. 7.3 029* 9 10.0 50.0 AIBN .085 5 hours C. 8.6 033* in aqueous 1 N sodium nitrate AIBN azohisisnbutyronilrile MEKP methyl ethyl kctonc peroxide measured as in Example I EXAMPLE 90 Parts of a sulfur dioxide-acrylamide copolymer, produced as in Example 1, analysis of which shows 37.96 percent carbon, 5.60 percent hydrogen, 13.86 percent nitrogen and 1 1.56 percent sulfur, are added to a suitable reaction vessel containing 72.5 ml. of 10 percentaqueous sodium hydroxide, a 10 percent excess of that calculated for total cleavage.

The vessel is heated to 82C. on a steam bath for 18 hours. The originally insoluble polymer rapidly dissolves to a clear solution.

The resultant solution is dried overnight to a white, brittle solid, 14.8 parts. The polymer is water-soluble and has an inherent viscosity in l N sodium nitrate of 0.05.

Infrared analysis shows the presence of carbonyl groups and the sulfinate group CSO Na. No S0 no 80;, and substantially no CONH groups are shown.

EXAMPLES 11-12 Substitution of equivalent amounts of potassium carbonate and barium hydroxide for the sodium hydroxide of Example 10, results in a similar product.

As mentioned briefly above, our novel acrylamide- SO polymers find utility as agents for increasing the wet strength and dry strength of paper. However, the polymers are not useful per se for this purpose. They first must be modified by chemical reaction and preferably -also rendered anionic.

According to the instant invention, the acrylnmidesulfur dioxide polymers are first reacted .with glyoxal under known reaction conditions. US. Pat. No. 3,556,932 sets forth the technique for conducting such reactions and said patent is therefore hereby incorporated herein by reference.

The reaction of the acrylamide-sulfur dioxide polymer with the glyoxal incorporates CHOHCHO groups onto the polymer through reaction with CONH (amide) groups of the polymer. The resultant polymers are thereby rendered thermosetting provided that at least about 0.1 CHOHCHO groups per glyoxal reactive -CONH group in the polymer are present.

The reaction of the acrylamide-sulfur dioxide polymer with glyoxal is conducted by heating a solution of the glyoxal and the polymer until a significant increase in viscosity is observed. The resultant solution can be cooled to ambient temperature and stored until required. During the reaction, not all of the glyoxal is reacted and generally only up to about one-half of the amount charged reacts. Of the halfthat reacts, most reacts to the extent of only one of its functionalities, thereby introducing the CHOHCHO groups onto the polymer. A small amount ofglyoxal reacts at both of-its functionalities so as to cross-link two polymer molecules and thereby cause the increase in viscosity mentioned above. If the resultant glyoxalated polymer is to be used to treat paper-making fibers, the unreacted glyoxal need not be eliminated from the solution since it is not substantive to the fibers in normal beater addition applications. As a general rule, one mole of glyoxal should be charged to the reaction vessel for every two or more glyoxal-reactive amino groups in the polymer being glyoxalated.

The glyoxal may be reacted with the acrylamidesulfur dioxide polymer before or after the polymer is rendered anionic, the anionic products being preferred for imparting wet and dry strength to paper.

The polymers may be rendered anionic utilizing any procedure known to those skilled in the art. lllustrative of such procedures are incorporation of anionic groups into the polymer such as by copolymerization of the acrylamide and sulfur dioxide with a water-soluble vinyl compound e.g., acrylic acid, methacrylic acid. vinylbenzene sulfonic acid, as mentioned above. Additionally, the anionic substituents may be formed in situ on the acrylamide-SO polymer per se by partial hydrolysis thereof to convert the CONH groups to (OOH groups or salts thereof. Additionally, ester comonomers may be copolymerized with the acrylamide-sulfur dioxide polymer and subsequently hydrolyzed with acid to COOH groups.

A third and more preferable method for incorporating anionic groups onto our novel acrylamide-SO polymers is by reaction thereof with a bisulfite of an alkali metal, such as sodium bisulfite, potassium bisulfite and the like to incorporate CHOHSO X groups thereon, X being hydrogen or an alkali metal.

The glyoxalated polymers are conveniently employed in the manufacture of wet and dry-strength paper as dilute aqueous solutions. The solutions can be applied to pre-formed paper by the well-known tub method, but, more preferably are applied by adding them directly to paper-making fibrous suspensions at any point in the paper-making process where wet and dry-strength additives are usually charged.

The glyoxalated polymers are rapidly and substantially adsorbed by the fibers at pH values the'range of 3.5 to 8.0. the use ofa retention aid being necessary in the case of beater additions of the polymer. A substantial amount of wet and dry strength is imparted when the amount of polymer adsorbed by the fibers is as little as 0.1 percent of the dry weight of the fibers, smaller or larger amounts up to about 2.0 percent are tolerable.

When retention aids are used, alum is preferred. The alum may be added to the paper fibers before or after the addition of the polymer in amounts known to those skilled in the art. Additionally, other known retention aids such as adipic acid-diethylenetriamineepichlorohydrin resins (U.S. Pat. No. 2,926,154), polyethyleneimine, alkylene polyamine resins (US. Pat. No. 3,248,353), polyvinylpyridine quaternized with butyl bromide and the like may be used.

As above, the following examples are set forth for purposes of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by weight unless otherwise specified.

EXAMPLE 13 To a suitable reaction vessel are added 15 parts of a 7.9 to 1 acrylamide-sulfur dioxide copolymer prepared as in Example 9. Parts of hot water containing 1.5 parts of 0.1 M sodium acid phosphate buffer are added to dissolve the copolymer. To the resultant solution is added 13.7 parts ofa 40 percent aqueous glyoxal so|ution. The pH is adjusted to 7.3 with potassium carbonate solution. The viscosity of the resultant reaction mixture increases rapidly at 25C. indicating attachment of the glyoxal to the amide units of the polymer with some cross-linking. After 1 hour at 25C., a Gardner Holdt reading of T is observed. The solution is then diluted with aqueous acid to bring the total solids to 1.5 percent and the pH to 3.5. The solution is designated as thereof and retention aids added are set forth in Table Solution I. ll], below.

In each instance. the Burst Strength (psi) and Wet EXAMPLE I4 Tensile Strength (lbs/in.) of the resultant paper hand- To 70 parts of Solution 1 are added small portions of sheets were equivalent to those of the products of Exsodium bisulfite until the bisulfite/total glyoxal (reamples l5 and 16 of Table ll. acted and unreacted) ratio is 1:] molewise. The bisul- TABLE "I fite powder dissolves and reacts with a concurrent increase ln pH from 3.5 to 4.8. The pH is then ad usted Treated q Polymer to 5.6 with a few drops of dilute sodium hydroxide solu- Polymer of as in Appued Rmmiun tion and the resultant solution is designated as Solut|on Ex. Example No. Ex. No. in Fibers Aitl 'z l8 1 l3 .40 alum .35

4 4 8 d EXAMPLES -16 53 7 3., 3

7 To an aqueous furnish at 0.6 percent consistency 5 :2 g composed ofa mixture of bleached hard wood and soft 23 8 I4 .35 do. d d 24 9 I3 .37' do. wood kraft paper fibers beaten to a Canadian stan ar freeness of 505 ml, are added sufficient amounts of Solution 1, above, so that the total amount of polymer we claim based on fiber is 0.5 percent. The same is done to a sec- I 0nd furnish with Solution 2, above. The mixtures are An ohgomer hdvmg the formula each adjusted to pH 7.0 by use of dilute sodium acid phosphate and sodium hydroxide solutions and hand- 000M (000M M sheets are formed in diluted condition from each. The

25 110- CH- CH; CH- CH CH- CH SO M wet handsheets are pressed between blotters and dried for one minute on a rotary laboratory drum dryer at n 240F. Two sheets of 65-70 pound basis weight paper a H W are formed. The results of testing on these sheets are wherein n is a whole, positive integer of 1-9, inclusive, set forth in Table ll, below. and M is an alkali metal or alkaline earth metal.

TABLE ll Polymer Percent Basis Burst Wet Tensile Solution Polymer Weight- Strength- Percent Strength Ex. No. Applied Retention Aid 70 lbs. psi Improvement lbs/in.

l5 l .35 Amine resin .15 69.3 49.7 20 3.23 lo 2 .35 do. 67.3 5l.2 23 3.74 l7 65.0 41.6 0.97 (Comp Commercially available polyaminc resin whic h when used alone produces no wet or dry strength improvement.

Following the procedures of Examples l3 and 14, 2. An oligomer according to claim 1 wherein M is an various of the polymers of Examples l-8 were treated alkali metal. and utilized to improve paper-making fiber as in Exam- 3. An oligomer according to claim 1 wherein M is soples l5 and 16. The polymers utilized. the amounts dium. 

1. AN OLIGOMER HAVING THE FORMULA
 2. An oligomer according to claim 1 wherein M is an alkali metal.
 3. An oligomer according to claim 1 wherein M is sodium. 